1. EÐL620M / Life in the Universe
Astrophysics – chemistry – Biology – earth-/planetary sciences
Atoms - chemical bond
Carbon chemical bond
Atoms and molecules in space;
Informations derived from spectroscopy
Molecules in the universe;
Existance and formation
Interactions between light and matter ;
photochemistry, photoionization,
photofragmentation
Thermochemistry in the Universe
Biochemistry

2. H H H2
A B AB

3. Et U
Ekin
Ekin U U
Ekin
A B
A - B
rAB

4. Et DE U
Ekin
A B
C*, (EC+DE)
C, (EC)
A - B
rAB

5. A B Et
A - B
rAB
A + B + C AB + C

6. +
A B C
A-B C
A B ?
A-B ?
A B M(s)
A-B M(s)
EAB EM + DE -

7. A B M(s)
A-B M(s)
M(s)
e.g. M(S) = “dust” = particles in space

8. “dust” / particles act as catalysis for molecular formation
“dust”: ca. 1% of compounds in ISM “dust”: typically 0.1 – 1 mm

9. “dust” ?
Cold clouds
Solid states compounds

11. C
Atom + atom Molecule
M(s)
but:
Atom + molecule Molecules
Molecule + molecule Molecules
e.g.
Exchange reactions:

12. C
Atom + atom Molecule
M(s)
but:
Atom + molecule Molecules
Molecule + molecule Molecules
e.g.:
Exchange reaction:
e.g.:
A H3CB ACH3 + B

13. C
Atom + atom Molecule
M(s)
En:
Atom + molecule Molecules
Molecule + molecule Molecules
e.g.:
Addition:
H2C=CH2 + AB H2AC-CH2B

14. Molecules in MC 12 different Atoms
Most common: H, C, N & O : “CHON”

15. GMC / hot cores: »106 molec/cm3
T » 102 (<103)K
T » K
T » 300 K
ISM: »1 molec/cm3
Earth/surface: »1019 molec/cm3

17. Collisions between
particles
needed for reactions
Collision frequency
A + B / ZAB
A + A / ZAA (no. of collisions
per sec
per volume unit):
ZAA µ size/ dA2
ZAA µ velocity A = v(T, mA)
ZAB µ [A] [B]
ZAA µ [A]2 d

18. T, mA const.: Z´AA = [A]2
GMC / hot cores: »106 molec/cm3
Z´AA = 1012
Z´AA = 1
Z´AA = 1038
ISM: »1 molec/cm3
Earth/surface: »1019 molec/cm3
-and in GMC / ISM: A = H (?)

19. A + M ???
M1 + M ???
A + B C + D

20. A + M ???
M1 + M ???
A + B C + D

21. A + M ???
M1 + M ???
A + B C + D

22. A + M ???
M1 + M ???
A + B C + D
Rate µ ZAB
Rate µ f (No. of molecules with enough energy to
exceed activation energy)
Rate µ f ZAB

23. A + M ???
M1 + M ???
A + B C + D

24. A + M ???
M1 + M ???
A + B C + D
Cross section = s = <d>2p d
But ions:

25. But ions:
A+ + B C + D +
F µ 1/r2 - + +

26. But Ions:
A+ + B C + D + - + +

27. + + But ions: A+ + B C + D Collision frequency much larger
Ion reactions very important in space

28. + A + M ??? M1 + M2 ??? A + B C + D Ions: Collision cross section =
s >> <d>2p d

29. A + M ???
M1 + M ???
A + B C + D
Rate µ ZAB
Rate µ f (No. of molecules with enough energy to
exceed activation energy)
Rate µ f ZAB

30. T Ea Orka, E Reaction coordinate A + B -> C + D f = exp(-Ea/kBT)

31. H2C=CH2 + AB H2AC-CH2B Ea

32. H2C=CH2 + AB H2AC-CH2B Ea
Catalysis
effect

34. T Ea Orka, E Reaction coordinate A + B -> C + D f = exp(-Ea/kBT)

35. Ea Small Energy, E Reaction coordinate Radicals A. .B H. .OH Cl. .CH3
-reactivity determined by electron pairing
A B A:B
+ .OH H:OH
Cl CH Cl:CH3
Unpaired electrons enhance reactivity
Energy, E
Reaction coordinate
A B
A:B
Ea Small
f =exp(-Ea/kBT) » 1